Radioactive nuclides are used for basic research and testing purposes in fields such as medicine, pharmaceuticals, genetics, molecular biology, cancer research and AIDS research. Radionuclides are used, for example, for imaging, radioimmunoassays and other assays for viruses, bacteria, antigens or antibodies; for labeling proteins, antibodies or radiopharmaceticals and for myriad other uses. Most of the radionuclides used for these purposes are "low level" isotopes which generally have half-lives of less than 50 years. About 97% of low level waste consists of radionuclides with half-lives of less than 10 years.
Disposal of low level radioactive waste is becoming more and more difficult. Radionuclides used in research, treatment and testing by hospitals, research laboratories and biotechnology companies are essential to their continued productivity. More than eighty percent of funded biomedical research utilizes radioactive isotopes.
The availability of radioactive waste disposal is diminishing and the cost is escalating. Many users are forced to maintain facilities for storing radioactive waste on site until it decays sufficiently to be disposed as conventional waste, which may take years. Such facilities are expensive to build and operate.
Methods currently used to handle radioactive waste are either very costly, or impractical for many users. For example, in U.S. Pat. No. 3,663,817, Sayers describes a method for storing radioactive waste by placing the waste in carriage containers which are mounted on storage racks. The containers are moved along the racks for a time necessary to ensure decay of the radioactive waste to safe levels. The method requires a complex and expensive apparatus and sufficient space to set up and operate the apparatus.
In U.S. Pat. No. 4,290,908, Horiuchi et al. describe a method and apparatus for treating and storing radioactive waste in which the material is dried to a powder and pelletized, and the pellets are stored until the radioactivity is reduced to safe levels. The pellets are then sealed in a vessel with a binder and the entire package is disposed.
Ernst in U.S. Pat. No. 4,357,541 describes a method for storing radioactive waste having very short half-lives. The waste is dropped into a bag in a compartment which is then closed and the device is rotated. At the end of the rotation, the bag is dropped through the bottom of the compartment into a receptacle to be disposed as ordinary waste.
Szulinski in U.S. Pat. No. 4,710,802 describes a storage depot for radioactive wastes consisting of holes drilled in the soil containing receptacles for storing the waste. The container is sealed and buried until the radioactive decay has declined to safe levels.
None of these prior methods or devices provides a continuous method for systematically disposing of radioactive waste. A system for safely and efficiently managing low level radioactive waste is urgently needed.